A former high-ranking Australian Navy officer has pleaded not guilty to eight charges of historic child sex offences in Darwin's Supreme Court.

Key points:

The charges relate to alleged incidents in the NT between 2004 and 2006, when the two complainants were children

Both complainants are now adults

Defence lawyer Thomas Berkley says his client is not guilty and will take the stand to "answer each and every allegation"

David Graham, 50, has been charged with three counts of indecent dealing with a child under 10 years, three act of gross indecency — including one charge relating to a child under 16 — aggravated assault, and attempted sexual intercourse.

He has been extradited to Darwin from Canberra to face court.

The charges against him relate to alleged incidents in the Northern Territory between 2004 and 2006, when the two complainants were children.

Both boys are now adults.

Prosecutor Stephen Geary delivered an opening address to the 14 jurors on Wednesday, outlining the allegations before the two complainants gave evidence in closed court.

Mr Geary told the court the two complainants, who cannot be identified, kept the allegations to themselves until several years after the alleged incidents occurred.

One of the complainants, who is now a young man, said he recalled three incidents in which Mr Graham allegedly touched his genitals when they were alone together.

In his opening address, Mr Geary told the jury the complainant recalled waking up one night to find Mr Graham, who he believed had been drinking, fondling his genitals.

"The accused was too drunk to drive home and he came into [the boy's] room late at night," Mr Geary told the court.

He said Mr Graham left the room once the child woke up.

Court hears of multiple instances of molestation

Mr Geary also gave a brief outline of the allegations made by the second complainant, who said Mr Graham attempted to rape him while they were alone together on a road trip.

The second man also alleged that once when he stayed over at Mr Graham's house, the man allegedly touched his genitals while they watched a movie together.

"The accused sat with him on the couch, put his arms around him and moved his hands inside his shorts," Mr Geary said.

"[The complainant] went to a spare room and locked the door, but it was a simple lock that could be opened from the outside."

The complainant said he later went to bed and locked his door, but woke to Mr Graham in his bed, masturbating.

In another instance, Mr Geary said, a complainant’s mother walked into a bedroom to see Mr Graham and her son playing video games while Mr Graham allegedly had two fingers down the back of the boy's shorts.

Afterwards, she took her son for a walk on the beach and spoke to him about inappropriate touching, but the boy told her nothing had happened, Mr Geary said.

Military police were alerted to the allegations in 2017, the court heard.

Both complainants gave evidence and answered questions in the closed courtroom.

Defence lawyer Thomas Berkley said his client was not guilty and would take the stand to "answer each and every allegation".